FR2947952A1 - PHOTO-DETECTOR DEVICE AND METHOD FOR PRODUCING A PHOTO-DETECTOR DEVICE - Google Patents

Abstract

A photo-detector device (100) having a plurality of pixels (101a-101b), each pixel comprising at least one alternating stack of a plurality of photodiodes and a plurality of electrodes (112, 118a-118c) based on an electrically conductive material, each photodiode comprising at least one intrinsic amorphous semiconductor layer (114a-114c) arranged in contact with at least one doped amorphous semiconductor layer (116a-116c) distinct from the amorphous semiconductor layers of the other photodiodes, each photodiode being disposed between at least two electrodes, and each pair of photodiodes having at least one of the electrodes disposed between these photodiodes.

Description

PHOTO-DETECTOR DEVICE AND METHOD FOR PRODUCING A PHOTO-DETECTOR DEVICE

TECHNICAL FIELD The invention relates to the field of photo-detector devices, or microelectronic image sensors, and more particularly that of color photo-detector devices of the type above IC, that is to say comprising a part photodetector disposed above an integrated circuit performing a treatment of electrical charges generated by the photodetector portion. The invention also relates to a method 15 for producing such a photo-detector device, especially of the type above IC. STATE OF THE PRIOR ART There are several types of microelectronic image sensors 20 - the so-called CCD sensors (Coupled Charges Device) generating, from light photons received by the sensor, electron-hole pairs by photoelectric effect in a semi substrate. crystalline driver, then collecting the electrons in potential wells, the so-called CMOS (Complementary Metal Oxide Semiconductor) or APS (Active Pixel Sensor) sensors in which each collection zone of 2 charges generated in a semiconductor crystal is accompanied by an amplifier, the so-called above IC sensors, part of the family of CMOS sensors, where the charges are generated in one or more photo-detector materials placed above an integrated circuit serving mainly to amplifier. In order to determine the colorimetric coordinates, such as those conforming to CIE XYZ, RGB or Lab standards, of a received light, the microelectronic image sensors are generally equipped with colored filters, generally 3 or 4, placed side by side. coast on different photo-detectors of the sensor. The document A highly reliable Amorphous Silicon photosensor for above IC CMOS image sensor "by N. Moussy et al., International Electron Devices Meeting 2006, IEDM'06, December 11-13, 2006, pages 1-3, describes such a sensor. images, which is also shown in Figure 1 and having the reference 1.

This image sensor 1 consists of two parts: the integrated circuit and the retina disposed above the integrated circuit (above IC). The integrated circuit comprises a substrate 2 on which CMOS transistors 4 are made. A dielectric layer 6 covers the CMOS transistors 4. Several layers of electrical interconnections, electrically connected to one another and to the CMOS transistors 4, are formed in the layer. In the example of FIG. 1, the sensor 1 comprises a first interconnection layer 8 and a second interconnection layer 10. The retina, formed by the 3 elements disposed above the dielectric layer 6, comprises several lower electrodes 12, for example based on chromium. Each pixel of the sensor 1 comprises one of the lower electrodes 12. These lower electrodes 12 are electrically connected to the second interconnection layer 10 and covered by a thick layer of intrinsic amorphous silicon 14 itself covered with a thin layer of amorphous silicon doped 16. A transparent upper electrode 18, based on ITO (indium tin oxide) and common to all the pixels of the sensor 1, is disposed on the thin layer of doped amorphous silicon 16. A passivation layer 20 separates colored filters 22 (one filter per pixel, and arranged for example according to a Bayer filter) from the upper electrode 18. The color filters 22 are covered with a planarization layer 24 on which microlenses 26 ( one per pixel) are arranged. Since the amorphous silicon layers 14 and 16 have different dopings (one being intrinsic and the other doped), they form a metallurgical junction, and therefore a photodiode. The light absorbed in these amorphous silicon layers 14, 16 generates electric charges which are then separated by the electric field present in the photodiode. The collected charges constitute the electrical signal which is then amplified by the integrated circuit of the sensor 1. In such an image sensor, the color filters absorb more than two-thirds of the light received by the sensor. Only one third of the light received 4 is therefore usable to perform the actual photo-detection. It is also known to produce color image sensors that do not include color filters. For example, the document US 2005/0205958 A1 describes an image sensor that does not include color filters, but in which are stacked different photodetector layers. This sensor further comprises a large number of electrodes in the form of electrically conductive layers, separated from each other by dielectric layers and interposed between the photodetector layers. In such a stack, the making of the electrical connections between the electrodes and the amplifiers of the integrated circuit is complex and restrictive. In addition, the electrical insulation of these connections is a problem because they add many steps to the method of producing the device with respect to a method for producing a sensor comprising colored filters, which substantially increases the cost of production of such a sensor with respect to a color filter sensor. SUMMARY OF THE INVENTION An object of the present invention is to provide a photo-detector device, or image sensor, for example of above IC type, whose structure facilitates in particular the realization of electrical connections with the part of the device carrying out the photo-detection, and that is inexpensive to achieve. For this purpose, the present invention proposes a photo-detector device comprising a plurality of pixels, each pixel comprising at least one alternating stack of several photodiodes and several electrodes based on an electrically conductive material, each photodiode comprising at least one layer. intrinsically amorphous semiconductor device disposed in contact with at least one doped amorphous semiconductor layer separate from the amorphous semiconductor layers of the other photodiodes, each photodiode being disposed between at least two electrodes, and each pair of photodiodes comprising at least one of the electrodes disposed between these photodiodes. An intrinsic amorphous semiconductor corresponds to an undoped amorphous semiconductor, that is to say having not undergone a voluntary addition of dopants.

This photo-detector device thus comprises a photo-detector structure comprising several layers of amorphous semiconductor, for example amorphous silicon, possibly continuous, between electrodes that can be based on an electrically conductive material and transparent to the lengths of waves to be detected, for example based on ITO. In this stack, there is therefore an alternation electrode - photodiode - electrode - photodiode - Thus, two photodiodes of the stack adjacent one above the other are separated from each other by one of the 6 electrodes based on the electrically conductive material. Thus, the invention proposes a photo-detector device, for example of the type above IC, which does not include color filters and makes it possible, for example, to obtain the colorimetric coordinates, for example those conforming to CIE XYZ, RGB or Lab standards. , the light received by the photodetector device, or the thermal image of a scene.

The size of the transparent electrodes may in particular delimit the pixels in the photo-detecting part of the device, that is to say have dimensions slightly smaller than the size of the pixels.

Since the amorphous semiconductor is a poor electrical conductor when it is intrinsic and unlit, it electrically insulates the electrodes in shaded or unlit areas, i.e. around the electrodes. Thus, the photo-detector device according to the invention does not require dielectric layers to electrically isolate the electrodes because this role of insulation is filled by the unlighted amorphous semiconductor portions around the electrodes.

The photo-detector device according to the invention also does not require additional layers or dielectric portions to electrically isolate electrical connections that can be made through the amorphous semiconductor layers to make electrical contact with the electrodes without steps. specific insulation for these 7 connections. In addition, this absence of dielectric layers in the photo-detector structure of the invention makes it possible to increase the effective surface area dedicated to the collection of light relative to the surfaces dedicated to the collection of light in the devices of the art. prior. With respect to a photo-detector device comprising color filters, the photo-detector device according to the invention can have pixels of larger sizes, that is to say whose dimensions which are substantially perpendicular to the light rays received by the sensor are greater than these same pixel dimensions of the photo-detector devices with colored filters, because in the invention, each pixel delivers several signals (a signal per photodiode), for example at least two, making it possible to retrieve the colorimetric coordinates of the received light, while four pixels are needed in a photo-detector device comprising color filters arranged according to a Bayer filter to obtain the same information. The detector material may be chosen such that it is sensitive only to the light spectrum intended to be detected by the photo-detector device. In the case where the photo-detector device is intended to perform color detection in the wavelength range of visible light (between about 380 nm and 780 nm), the amorphous semiconductor may be silicon because this semiconductor is infrared transparent, and the optics, for example microlenses, which can be coupled to the photodetector device are generally opaque to ultraviolet. Thus, only the visible spectrum will be detected by the photo-detector device without the addition of additional filtering means that are conventionally associated with the Bayer filters of the prior art. Each pixel of the device may comprise a stack of at least two photodiodes. In each pixel, each electrode may comprise at least one portion of the electrically conductive material not superimposed on the other electrodes of the pixel and electrically connected to at least one interconnection hole, or via, passing through the amorphous semiconductor layers and said non-electrically conductive portion. superimposed on the other electrodes, the via hole being filled with at least one electrically conductive material. Thus, it is possible to make electrical connections in the form of nias, these connections being connected to the electrodes of the photo-detection device and not requiring electrical insulation elements other than the amorphous semiconductor layers. The device may further comprise at least one integrated circuit electrically connected to at least one electrical interconnection layer disposed between the integrated circuit and the photodiode stack, the electrically conductive material of the vias being electrically connected to at least the layer of electrical interconnections.

In each pixel, one of the electrodes may be disposed between the electrical interconnection layer 9 and the photodiode stack, and the other electrodes of the pixel may be based on at least one wavelength-transparent material for to be detected by the photodiodes.

The electrically conductive material of the vias may be electrically connected to the electrical interconnection layer through at least a portion of electrically conductive material disposed at one of the electrodes between the interconnect layer. and the stack of photodiodes. In each pixel, portions of an electrically conductive material may be substantially superimposed on said electrode portions not superimposed on the other electrodes of the pixel, the amorphous semiconductor layers being able to be disposed between said portions of electrically conductive material and the electrical interconnections. In each pixel, the electrodes may be electrically insulated from the electrodes of the neighboring pixels by portions of the amorphous semiconductor layers and / or portions of at least one dielectric material disposed between the stacks of photodiodes of two neighboring pixels. The intrinsic amorphous semiconductor layers and / or the doped amorphous semiconductor layers may be common to several pixels of the device. At least one of the electrodes may be common to several pixels of the device. The device may further comprise at least one passivation layer covering the stack 5 of photodiodes. Each pixel may comprise at least one micro-lens disposed on the passivation layer. The amorphous semiconductor layers may be based on Si: H (hydrogenated silicon), and / or Ge and / or SiGe and / or CdTe: O (oxygenated cadmium telluride) and / or AsGa. Intrinsic amorphous semiconductor layers may be in contact with the electrodes via at least one layer of an electrically conductive material or doped amorphous semiconductor. The present invention also relates to a method for producing a photo-detector device comprising a plurality of pixels, the method comprising, for each pixel, the production of at least one alternating stack of several photodiodes and of several electrodes based on an electrically conductive material, such that each photodiode comprises at least one intrinsic amorphous semiconductor layer arranged in contact with at least one doped amorphous semiconductor layer distinct from the amorphous semiconductor layers of the other photodiodes, each photodiode being disposed between at least two electrodes, and each pair of photodiodes 30 having at least one of the electrodes disposed between these photodiodes. At least a portion of the electrodes and / or the amorphous semiconductor layers may be produced by the implementation of a step of depositing the material of the electrodes or of the amorphous semiconductor, then photolithography steps and etching the deposited material. The method may further comprise, for each pixel, the production of interconnection holes through electrode portions that are not superimposed on the other electrodes of the pixel and the amorphous semiconductor layers, and then the deposition of at least one material. electrically conductive in the vias. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood on reading the description of exemplary embodiments given purely by way of indication and in no way limiting, with reference to the appended drawings in which: FIG. 1 represents a CMOS image sensor of above type IC with colored filters according to the prior art, - Figure 2 shows a photo-detector type above IC without color filters, object of the present invention, according to a first embodiment, - Figures 3A and 3B represent a photo-detector device of above type IC without color filters, object of the present invention, according to a second embodiment, 12 - Figure 4 represents a photo-detector device of type above IC without color filters, object of the present invention according to a third embodiment, FIGS. 5A to 5C show top views of four pixels of different devices above-IC photo-detectors without color filters, object of the present invention, according to several embodiments. Identical, similar or equivalent parts of the different figures described below bear the same numerical references so as to facilitate the passage from one figure to another. The different parts shown in the figures are not necessarily in a uniform scale, to make the figures more readable. The different possibilities (variants and embodiments) must be understood as not being exclusive of each other and can be combined with one another. DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS Referring firstly to FIG. 2 which represents a photo-detector device 100, or image sensor, of the above IC type, according to a first embodiment, not including colored filters. In a similar manner to the previously described sensor 1 of the prior art, the photo-detector device 100 is composed of two parts: a photo-detection portion 13 formed by a retina and a portion of electric charge processing generated by the retina formed in particular by an integrated circuit, the retina being disposed above the integrated circuit (above IC). The integrated circuit comprises a substrate 102, for example based on silicon, on which CMOS transistors 104 are produced. A dielectric layer 106, for example based on SiO 2, covers the CMOS transistors 104. Several layers, or levels, of Electrical interconnections, electrically connected to each other and to CMOS transistors 104, are formed in the dielectric layer 106. In the example of FIG. 2, the sensor 100 comprises a first interconnection layer 108 and a second interconnection layer. 110. The retina, formed above the dielectric layer 106, has lower electrodes 112 disposed on the dielectric layer 106. In this first embodiment, each pixel of the sensor 100 includes a lower electrode 112. These lower electrodes 112 can be based on an electrically conductive material that can absorb light, such as graphite and / or graphen, or reflect light e, such as metal (for example aluminum and / or chromium and / or copper and / or tungsten and / or titanium), or a material transparent to light such as ITO and / or SnO2: F and / or Cd2SnO4 and / or Zn2SnO4 and / or ZnO. The choice of the material of the lower electrodes 112 is made in particular according to the optical conditions imposed by the nature of the semiconductor disposed on these electrodes. Depending on the absorption capacity of the semiconductor, the material of the first electrode will be chosen to be reflective to increase the signal of the device, or absorbent if this signal is sufficient. In each pixel of the device 100 (two pixels 101a and 101b are shown in FIG. 2), each of the lower electrodes 112 is covered by a stack of layers forming several photodiodes, for example three in the example of FIG. 2. Each photodiode comprises an intrinsic amorphous semiconductor layer 114a, 114b, 114c disposed in contact with an n-type or p-type doped amorphous semiconductor layer 116a, 116b, 116c. A transparent conductive electrode 118a, 118b, 118c is also disposed in contact with each of the doped amorphous semiconductor layers 116a-116c. The amorphous semiconductor may be Si: H, Ge, SiGe, CdTe: O or AsGa. In addition, in the example of FIG. 2, the amorphous semiconductor layers 114 and 116 are continuous between the pixels of the sensor 100, that is to say common for all the pixels of the sensor 100. The electrodes 118a -118c have for example a thickness (dimension along the y-axis shown in Figure 2) between about 30 nm and 300 nm when these electrodes are based on a transparent conductive material such as ITO. In a variant, it is possible to produce the electrodes 118a-118c in the form of a layer of metal, for example based on aluminum and having a thickness of between approximately 1 nm and 20 nm. In another variant, it is also possible for each of the electrodes 118a-118c to be formed by a stack of several layers of electrically conductive materials transparent to the light received by the photo-detector device 100. The size of the electrodes 118a-118c, which is substantially similar for all the photodiodes and all the pixels, delimits the size of the photosensitive areas of the sensor 100. In order to improve the electrical contact between the electrodes 118a-118c and the doped amorphous semiconductor layers 116a-116c on which are disposed electrodes 118a-118c, it is possible that an electrically conductive layer, not shown in Figure 2, is disposed between an electrode 118a-118c and a doped amorphous semiconductor layer 116a-116c. In this case, the thickness of this electrically conductive interface layer is chosen to be sufficiently thin, that is to say of a thickness for example between about 1 nm and 20 nm, so that it is optically transparent. The intrinsic amorphous semiconductor layers 114a-114c and the very thin, therefore very weakly conducting, doped layers 116a-116c provide the electrical isolation between the electrodes lying on the same level, that is to say lying next to each other, between two neighboring pixels of the device. Thus, the first intrinsic amorphous semiconductor layer 114a provides electrical isolation 16 between the lower electrodes 112. The second and third intrinsic amorphous semiconductor layers 114b and 114c respectively provide electrical isolation between the electrodes 118a and the electrodes. electrodes 118b. The electrodes 118c are electrically insulated from each other by a dielectric layer 120 covering these electrodes 118c and which also forms a planarization layer on which micro-lenses 122 are arranged (one per pixel), each of these microlenses 122 enabling to concentrate the light received at each pixel on the photodiodes. In each pixel, each of the electrodes 118a-118c comprises a main portion, for example of substantially rectangular shape, and a portion of electrically conductive material not superimposed on the other electrodes of the pixel. These portions, offset relative to the other electrodes of the pixel, enable the electrodes 118a-118c to be electrically connected to the integrated circuit of the sensor 100 via interconnection holes, also called nias, for example metal-based and passing through the stacks of the amorphous semiconductor layers 114a-114c, 116a-116c to reach and be electrically connected to the interconnection layers 108, 110, while being electrically isolated from the other electrodes of the pixel. For the pixel 101a of the device 100 shown in FIG. 2, the first electrode 118a includes such a portion 126a which is not superimposed on the electrodes 118b, 118c of the pixel 101a and 17 which is crossed by a metal via hole 124a. Thus, the via 124a passes through the stack of amorphous semiconductor layers 114a-114c, 116a-116c and electrically connects the first electrode 118a, through the portion 126a, to the second interconnect layer. 110 while being electrically isolated from the other electrodes 118b and 118c of the pixel 101a. Although not shown in FIG. 2, the other electrodes 118b, 118c of the pixel 101a also each comprise a portion of electrically conductive material not superimposed on the other electrodes of the pixel 101a and electrically connected to the interconnection layers 108 or 110 via a via via the amorphous semiconductor layers 114a-114c, 116a-116c while being electrically insulated from the other electrodes of the pixel 101a. For the pixel 101b of the device 100, the third electrode 118c has a portion 126c which is not superimposed on the other electrodes 118a, 118b of the pixel 101b and which is traversed by a via 124b. The via 124b passes through the amorphous semiconductor layers 114a-114c and 116a-116c and electrically connects the third electrode 118c, via its portion 126c, to the second interconnect level 110. Similarly, the other electrodes 118a, 118b of the pixel 101b also each comprise a portion of electrically conductive material, not shown in FIG. 2, not superimposed on the other electrodes of the pixel 101b and electrically connected to the interconnection layers 108 or 110 via a via via the amorphous semiconductor layers 114a-114c, 116a-116c without being in electrical contact with the other electrodes of the pixel 101b. Each via 124a, 124c has an upper portion 128a, 128c masking the portions 126a, 126c of the electrodes 118a, 118c of the light received by the device 100. In a variant, the vias 124a, 124b may not include these upper portions 128a, 128c. When the sensor 100 does not include microlenses 122, the vias are preferably made with such upper portions to mask portions of the pixel that are not intended to perform a photoelectric conversion of the light received , and this to prevent the amorphous semiconductor becomes conductive by the generated charges.

Thus, in each pixel of the device 100, several photodiodes (three in the example of FIG. 2) are formed stacked one above the other, each of the photodiodes being formed by the junction between one of the amorphous semiconductor layers. 114a-114c and one of the doped amorphous semiconductor layers 116a-116c. The light passing through these amorphous silicon layers 114a-114c, 116a-116c creates electrical charges which are then separated by the electric field present in the photodiodes. The collected electrical charges constitute the electrical signal which is conveyed to the transistors 104, that is to say to the integrated circuit of the device 100, via the interconnection holes, and then amplified by the integrated circuit of the photoelectric device. detector 100. Thus, for each pixel, as many electrical signals as photodiodes. In the device 100 of FIG. 2, since each photodiode is disposed between two electrodes, it is possible to collect the electric charges created despite the short life of these charges before their recombination and the low conductivity of the amorphous semiconductor. . In general, each pixel of the photo-detector device 100 may comprise n photodiodes as well as n + 1 electrodes, with n integer? 2. Although in the example of FIG. 2 each pixel of the device 100 comprises electrodes that are independent of one another, it is possible for electrodes of each pixel lying on the same level to be formed by an electrode common to several or all the pixels. The thicknesses of the various amorphous semiconductor layers are chosen according to their optical indices and the optical absorption laws of the different materials which are variable as a function of the wavelength of the light received. The total of these thicknesses is, for example, less than about 0.7 μm, and the thickness of each of the layers is, for example, between about 0.01 μm and 0.4 μm. The lengths and widths of the pixels 20 (corresponding to the dimensions in the (X, Z) plane shown in FIG. 2) are, for example, greater than about 0.7 μm, and generally about 2 μm. Since pixel aspect ratio and pixel aspect ratio are large, this gives the photodetector a better definition of colors and pixels. This also avoids that a photon arriving obliquely on the upper surface of a pixel is not immediately absorbed and therefore its trajectory ends its course in the pixel next door, unlike the photo-detectors of the camera. prior art in which the pixels are higher than wide (or long). The photo-detector device 100 thus makes it possible to avoid blurs that may appear on the images or iridescence at the limits of the colors. The thicknesses of the amorphous semiconductor layers of the different photodiodes of the same pixel are different from each other. These thicknesses are for example chosen such that they decrease in the direction from the integrated circuit of the device 100 to the passivation layer 120. Thus, the intrinsic amorphous semiconductor layer closest to the integrated circuit or the levels of interconnections (layer 114a in the example of Figure 2) therefore has the largest thickness. The intrinsic amorphous semiconductor layer closest to the light input face of the sensor 100 (layer 114c in the example of FIG. 2), or of the passivation layer 120, therefore has the smallest thickness . In the example of FIG. 2, the first layer 114a has a thickness of about 300 nm, the second layer 114b has a thickness of about 100 nm, and the third layer 114c has a thickness of about 15 nm.

From the signals coming from the three photodiodes of each pixel, the integrated circuit performs a calculation of three linear equations with three unknowns making it possible to obtain, with the minimum of error and noise, the colorimetric coordinates of the light received, for example according to the standards. of CIE 1931. FIGS. 3A and 3B show a photo-detector device 200 according to a second embodiment. With respect to the device 100 according to the first embodiment previously described, the doped amorphous semiconductor layers 116a-116c are not continuous from one pixel to another of the device 200. Each of these layers 116a-116c is formed by separate portions and not electrically connected to each other from one pixel to another. In addition, in this device 200, the lower electrodes 112 are replaced by a single electrode 202 common to all the pixels of the photo-detector device 200 and based on a non-transparent material to light. This lower common electrode 202 is interrupted at the vias 124a-124c which are electrically connected to contact pads 204 arranged at the same level as the lower common electrode 202 and providing the electrical connection between the vias 124a 124c and the interconnection layers 108, 110 of the photo-detector device 200. The vias 124a-124c 22 are also surmounted by upper portions 128a-128c based on the same material as that deposited in the vias. . This second embodiment makes it possible in particular to produce a lower electrode 202 based on a conductive material other than the transparent conductive material used to make the other electrodes 118a-118c. In this second embodiment, the vias 124a-124c are etched through the amorphous semiconductor layers 114a-114c, 116a-116c and through the portions 126a-126c to be electrically connected. at the vias 124a-124c.

These holes are etched, advantageously, with a single mask with stop at the contact pads 204. Finally, since the layers 116a-116c doped amorphous semiconductor are not continuous from one pixel to another of the device 200 but formed by separate portions and not electrically connected to each other from one pixel to another, the electrical insulation between the electrodes and the vias from one pixel to the other is therefore improved compared to device 100 according to the first embodiment. FIG. 3B is a perspective view of two pixels 201a, 201b of the photo-detector device 200. In this figure, the microlenses 122 are not represented. On the other hand, step transitions between the pixels are shown in FIG. 3B and not in FIG. 3A. In this second embodiment, it can be seen that each of the electrodes 118a-118c has a substantially rectangular main portion and is electrically connected to the second interconnection layer 110 via interconnected via holes 124a-124c. electrically to the portions 126a-126c of these electrodes. It is possible, however, that the electrodes have different surfaces and / or shapes, for example due to the passageways between the electrodes, while preferably having the largest possible surface area. Portions 212 of the intrinsic amorphous semiconductor layers 114a-114c, at the step passages formed in particular by the etched edges of the electrodes, provide electrical isolation between the electrodes 118a-118c of the adjacent pixels and between the holes. interconnection 124a-124c of the same pixel. It is possible that the common electrode 202 is electrically connected to the interconnection layer 110 by interconnection holes made at each pixel of the device 200. In a variant, it is also possible for the common electrode 202 to it is not electrically connected to the interconnection layer 110 at each pixel of the device 200, but only at a portion of the pixels of the device 200, or even when the material from which the common electrode 202 is made is highly conductive, for example aluminum, only in a single pixel of the sensor 200, through a single via. FIG. 4 shows a photo-detector device 300 according to a third embodiment. With respect to the two previous embodiments, the portions of amorphous silicon between the pixels of the sensor 300 (two pixels 301a, 301b are shown in FIG. 4) are etched and then filled with a dielectric material forming insulating portions 304. In the example of FIG. 4, the insulation portion 304 electrically isolating the pixels 301a, 301b is obtained from the material forming the planarization layer 120 covering the stacks of amorphous semiconductor layers. In this third embodiment, the photo-detector device 300 further comprises contact layers 306a, 306b, for example based on an electrically conductive material, covering the electrodes, here the electrodes 118a, 118b of the first two photodiodes. These contact layers 306a, 306b make it possible in particular to produce the transparent conductive electrodes 118a, 118b from a material having an electrical conductivity lower than that of the ITO. Thus, these electrodes 118a, 118b can be made for example from Sn doped In2O3, Al doped ZnO, F doped SnO, InZnO, InMoO, InTiO or Ta2O5. The thickness of these contact layers 306a, 306b is chosen to be sufficiently thin (thickness for example between about 1 nm and 20 nm) for these layers 306a, 306b to be transparent to light or to have negligible light absorption. and they can be etched together with the material of the electrodes 118a, 118b. The contact layers 306a, 306b are for example based on a transparent electrically conductive material (such as ITO), or based on a metal (for example Al and / or Ti and / or of W and / or Ta and / or Cr) or of an amorphous semiconductor doped, for example, with the type of doping reverse doping doped semiconductor layers 116a, 116b.

In this embodiment, the insulating portions 304 are in contact with the dielectric layer 106, providing electrical isolation between the pixel elements. In a variant, and in particular when the lower electrodes 302 are formed by a single electrode common to the various pixels of the device 300, it is possible for the insulating portions 304 not to pass through the lower electrodes 302 but to stop above these lower electrodes 302.

FIGS. 5A, 5B and 5C show top views of four pixels of different photo-detector devices, for example similar to devices 100, 200 and 300 previously described. In these figures, only the electrodes 118c at the apices of the photodiode stacks are shown. The electrodes 118c are electrically connected to the vias 124c. The vias 124a and 124b are electrically connected to the electrodes 118a and 118b (not shown). In the example of FIG. 5A, for each pixel of the photo-detector device, the interconnection holes 124a-124c are arranged at one side of the electrode 118c, this arrangement being able to be similar for all the pixels. of the photo-detector device. In the example of FIG. 5B, the four-pixel four-pixel via holes 124a-124c of the photo-detector are aligned with one another along an axis parallel to the X-axis shown in FIG. 5B. . This arrangement can be repeated for each group of four pixels of the device. In the example of FIG. 5C, the vias 124a-124c of each pixel are not aligned relative to one another, but arranged so that the vias 124a-124c are moved furthest apart. possible from each other, and this both between the vias of the same pixel and between the vias of neighboring pixels. The photo-detector devices 100, 200 and 300 described above can be implemented by implementing successive deposition, photolithography and etching steps on the integrated circuit, and more precisely on the dielectric layer 106, to carry out the stacking of photodiodes. After making the stack of photodiodes, the vias are formed through the amorphous semiconductor layers and the electrode portions not superimposed on the other electrodes of the pixel. An electrically conductive material is then deposited in the vias. The photo-detector device can then be completed by the implementation of conventional steps 27 for producing image sensors (planarization layer deposition, production of micro-lenses, etc.).

Claims (17)

REVENDICATIONS1. Photo-detector device (100, 200, 300) comprising a plurality of pixels (101a-101b, 201a-201b, 301a-301b), each pixel (101a-101b, 201a-201b, 301a-301b) comprising at least one stack alternating several photodiodes and several electrodes (112, 118a-118c, 202, 302) based on an electrically conductive material, each photodiode having at least one intrinsic amorphous semiconductor layer (114a-114c) disposed in contact with at least one doped amorphous semiconductor layer (116a-116c) separate from the amorphous semiconductor layers (114a-114c, 116a-116c) of the other photodiodes, each photodiode being disposed between at least two electrodes (112, 118a); 118c, 202, 302), and each pair of photodiodes having at least one of the electrodes (118b-118c) disposed between these photodiodes. 2. Device (100, 200, 300) according to claim 1, wherein each pixel (101a-101b, 201a-201b, 301a-301b) comprises a stack of at least two photodiodes. 3. Device (100, 200, 300) according to one of the preceding claims, wherein, in each pixel (101a-101b, 201a-201b, 301a-301b), each electrode (112, 118a-118c, 202, 302 ) comprises at least one portion (126a-126d) of the electrically conductive material not superimposed on the other electrodes (112, 118a-118c, 202, 302) of the pixel (101a-101b, 201a-201b, 29301a-301b) and electrically connected at least one via (124a-124d) passing through the amorphous semiconductor layers (114a-114c, 116a-116c) and said portion (126a-126d) not superimposed on the other electrodes (112, 118a-118c, 202, 302), the via hole (124a-124d) being filled with at least one electrically conductive material. The device (100, 200, 300) according to claim 3, further comprising at least one integrated circuit (102, 104) electrically connected to at least one electrical interconnection layer (108, 110) disposed between the integrated circuit ( 102, 104) and the stack of photodiodes, the electrically conductive material of the vias (124a-124d) being electrically connected to at least said electrical interconnect layer (108, 110). The device (100, 200, 300) according to claim 4, wherein in each pixel (101a-101b, 201a-201b, 301a-301b), one of the electrodes (112, 202, 302) is disposed between the electrical interconnection layer (108, 110) and the photodiode stack, and the other electrodes (118a-118c) of the pixel are based on at least one wavelength-transparent material to be detected by the photodiodes. The device (200, 300) according to claim 5, wherein the electrically conductive material of the via holes (124a-124d) is electrically connected to the electrical interconnect layer (108, 110) via at least one portion (204) of electrically conductive material disposed at said one of the electrodes (202, 302) between the electrical interconnection layer (108, 110) and the photodiode stack. 7. Device (100, 200, 300) according to one of claims 4 to 6, wherein, in each pixel (101a-101b, 201a-201b, 301a-301b), portions (128a-128d) of a electrically conductive material are substantially superimposed on said electrode portions (126a-126d) not superimposed on the other electrodes (112, 118a-118c, 202, 302) of the pixel (101a-101b, 201a-201b, 301a-301b), the layers amorphous semiconductor device (114a-114c, 116a-116c) being disposed between said portions (128a-128d) of electrically conductive material and the electrical interconnect layer (108, 110). 8. Device (100, 200, 300) according to one of the preceding claims, wherein, in each pixel (101a-101b, 201a-201b, 301a-301b), the electrodes (112, 118a-118c, 202, 302 ) are electrically insulated from the adjacent pixels (101a-101b, 201a-201b, 301a-301b) by portions (212) of the amorphous semiconductor layers (114a-114c) of adjacent pixels (112, 118a-118c, 202, 302). , 116a-116c) and / or portions (304) of at least one dielectric material disposed between the stacks of photodiodes of two neighboring pixels (101a-101b, 201a-201b, 301a-301b). 31 9. Device (100, 200) according to one of the preceding claims, wherein the intrinsic amorphous semiconductor layers (114a-114c) and / or doped amorphous semiconductor layers (116a-116c) are common to several pixels (101a-101b, 201a-201b) of the device (100, 200). 10. Device (200) according to one of the preceding claims, wherein at least one of the electrodes (202) is common to several pixels (201a-201b) of the device (200). 11. Device (100, 200, 300) according to one of the preceding claims, further comprising at least a passivation layer (120) covering the stack of photodiodes. 12. Device (100, 200) according to claim 11, wherein each pixel (101a-101b, 201a-201b) comprises at least one micro-lens (122) disposed on the passivation layer (120). 13. Device (100, 200, 300) according to one of the preceding claims, wherein the amorphous semiconductor layers (114a-114c, 116a-116c) are based on Si: H, and / or Ge and / or SiGe and / or CdTe: O and / or AsGa. The device (300) according to one of the preceding claims, wherein intrinsic amorphous semiconductor layers (114b-114c) are in contact with the electrodes (118a-118b) through at least one layer (306a, 306b) based on an electrically conductive material or doped amorphous semiconductor. 15. A method of producing a photo-detector device (100, 200, 300) comprising a plurality of pixels (101a-101b, 201a-201b, 301a-301b), the method comprising, for each pixel (101a-101b, 201a-201b, 301a-301b), the production of at least one alternating stack of several photodiodes and of several electrodes (112, 118a-118c, 202, 302) based on an electrically conductive material, such that each photodiode comprises at least one intrinsic amorphous semiconductor layer (114a-114c) disposed in contact with at least one doped amorphous semiconductor layer (116a-116c) separate from the amorphous semiconductor layers (114a-114c, 116a-116c ) other photodiodes, each photodiode being disposed between at least two electrodes (112, 118a-118c, 202, 302), and each pair of photodiodes having at least one of the electrodes (118b-118c) disposed between these photodiodes. The method of claim 15, wherein at least a portion of the electrodes (112, 118a-118c, 202, 302) and / or amorphous semiconductor layers (114a-114c, 116a-116c) are made by the implementation of a deposition step of the material of the electrodes (112, 118a-118c, 202, 302) or of the amorphous semiconductor, and then of photolithography and etching steps of the deposited material. 33 17. Method according to one of claims 15 or 16, further comprising, for each pixel (101a-101b, 201a-201b, 301a-301b), the realization of vias (124a-124d) through portions. electrodes (126a-126d) not superimposed on the other electrodes (112, 118a-118c, 202, 302) of the pixel (101a-101b, 201a-201b, 301a-301b) and the amorphous semiconductor layers (114a-201b); 114c, 116a-116c), and then depositing at least one electrically conductive material in the vias (124a-124d).